1. Field of the Invention
An aspect of the present invention relates to at least one of a device for correcting an edge portion of a sheet material and an electrophotographic image forming apparatus.
2. Description of the Related Art
As image forming apparatuses such as copying machines, printers, facsimile machines, and complex devices formed with those machines, various image forming apparatuses using electrophotographic techniques have been developed and have become publicly known arts. An image forming process used in such image forming apparatuses includes the following steps: forming an electrostatic latent image on the surface of a photosensitive drum serving as an image carrier, developing and visualizing the electrostatic latent image on the photosensitive drum with a developer such as toner, transferring the developed image onto a recording paper sheet (also referred to as a sheet material, a paper sheet, a recording material, or a recording medium) with a transfer device so that the recording paper sheet carries the image, and fixing the toner image on the recording paper sheet with a fixing device using pressure, heat, and the like.
In the fixing device, a fixing member (a fixing unit) formed with rollers or belts facing each other or a combination of the rollers and the belts is in contact with a pressure member (a pressure unit), to form a nip unit. A recording paper sheet is inserted into the nip unit, and heat and pressure are applied to the nip unit, to fix a toner image on the recording paper sheet.
Recording paper sheets used in image forming apparatuses are formed by cutting and dividing a base paper sheet into sheets of various sizes that have been standardized. At the time of processing, however, so-called “burrs” such as minute notches and scratches may appear at the cut edges of the recording paper sheets obtained by the cutting.
It is known that the burrs may cause the belts or the like of the fixing device to wear, and degrade printing quality. Particularly, it is known that burrs formed at the edges in the paper width direction, rather than burrs formed at the top and rear edges in the paper conveying direction, may leave streaky surfaces on the belts. Therefore, various edge correcting devices (burr squashing devices) for sheet materials have been suggested.
For example, Japanese Laid-Open Patent Application No. 2005-179041 discloses an image forming apparatus that corrects burrs by pressing a smoothing member (a roller) having an irregular surface against the burrs. Japanese Laid-Open Patent Application Nos. 2008-254887, 2010-150010, 2010-132403, and 2010-276846 also disclose burr removing devices and the like that remove burrs by inserting a paper sheet between two rollers to which a high pressure is applied.
However, it may not be possible to readily apply the techniques disclosed in the above mentioned patent literatures to various kinds of sheet materials of different sizes, and a problem may still remain that a load is applied to portions other than the edges of sheet materials. Therefore, sufficiently high efficiency may not have been achieved yet in squashing burrs.